China's Supercomputer Is Still Tops, But Benchmark Changes Are Coming

The annual Supercomputing show is this week in Denver and as usual it's time for the semi-annual listing of the world's fastest computers. The top of the list is unchanged from the June list but what's interesting is a plan from the folks who keep the Top 500 list of the world's fastest supercomputers to develop new benchmarks that may lessen the impact of accelerators such as Nvidia's Tesla series and Intel's Xeon Phi.

The annual Supercomputing show is this week in Denver and as usual it's time for the semi-annual listing of the world's fastest computers. The top of the list is unchanged from the June list but what's interesting is a plan from the folks who keep the Top 500 list of the world's fastest supercomputers to develop new benchmarks that may lessen the impact of accelerators such as Nvidia's Tesla series and Intel's Xeon Phi.

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As on the previous list, the fastest computer is the Tianhe-2, at the National Super Computer Center in Guangzhou, China, which is based at the National University of Defense Technology in Changsha, China. It shows sustained performance of more than 33.8 petaflops (trillion floating point operations per second) and peak performance of 54.9 petaflops on the Linpack benchmark. This has 16,000 nodes, each with two 12-core Intel Xeon E5-2692 processors and three Xeon Phi processors for a combined total of 3,120,000 computing cores. The next four supercomputers are the same as well: the Titan system at Oak Ridge National Laboratory, based on a Cray XK7 system with 18,688 nodes, each containing a 16-core AMD Opteron 6274 and an Nvidia Tesla K20x graphics processing unit (GPU) accelerator; the Sequoia system at the Lawrence Livermore National Laboratory, based on IBM's BlueGene/Q system and its Power CPUs; the K computer at Japan's RIKEN Advanced Institute for Computational Science based on Fujitsu SPARC64 processors; and the Mira system at Argonne National Laboratory, also based on the BlueGene/Q system.

The only new addition to the top 10 is the Piz Daint system at the Swiss National Supercomputing Centre, based on a Cray C30 system using Intel Xeon E5-2670s as well as Nvidia K20x accelerators.

It's interesting to note that 53 of the top 500 are using accelerators or co-processors, including 38 using Nvidia's Tesla chips, two using ATI, and 13 using Intel's Xeon Phi. Intel provides the processors for 82.4 percent of the top 500 systems, and 94 percent of the systems use processors with six or more cores. Of the top 500 systems, 265 are located in the United States, 102 systems in Europe, and 115 in Asia.

One new wrinkle: The organizers of the top 500 list released a new benchmark called the High Performance Conjugate Gradient (HPCG), which is designed to supplement Linpack in such rankings at some future point. In a paper describing HPCG, the authors Jack Dongarra of the University of Tennessee and Michael Heroux of Sandia National Laboratories point out the limitations of the Linpack benchmark in predicting the performance of systems with accelerators on most kinds of real-world calculations. In particular, they note the numbers for the Titan system reflect what happens when all the data and all the floating-point applications are resident on the GPUs; but in the real world, most applications run solely on the CPUs and selectively off-load some computation to the GPU.

Even the authors of the new benchmark note it will take a long time for it to gain traction, and that it is just entering beta. But I always think benchmarks that more closely match how real people use the systems are better, so this seems like a step in the right direction. This could dramatically change how we think about the fastest systems in the years to come.

Of course, another important metric these days is how much power you need to get a certain level of performance. For that, there's the Green 500 list, which ranks supercomputers on performance per watt. The June list was topped by the Eurora system at Italy's Cineca, based on a Eurotech Aurora system with 8-core Xeon E5-2687W processors and Nvidia K20 GPUs, which predicts 3,208.83 megaflops per watt. The November update of the Green 500 should be out shortly.

Michael J. Miller's Forward Thinking Blog: forwardthinking.pcmag.com
Michael J. Miller is chief information officer at Ziff Brothers Investments, a private investment firm. From 1991 to 2005, Miller was editor-in-chief of PC Magazine, responsible for the editorial direction, quality and presentation of the world's largest computer publication.
Until late 2006, Miller was the Chief Content Officer for Ziff Davis Media, responsible for overseeing the editorial positions of Ziff Davis's magazines, websites, and events. As Editorial Director for Ziff Davis Publishing since 1997, Miller took an active role in...
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